#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    vector<vector<int>> matrixBlockSum(vector<vector<int>>& mat, int k) {
        int m, n;
        m = mat.size();
        n = mat[0].size();
        vector<vector<int>> dp(m + 1, vector<int>(n + 1));
        for (int i = 1;i <= m;i++)
        {
            for (int j = 1;j <= n;j++)
            {
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1] - dp[i - 1][j - 1] + mat[i - 1][j - 1];
            }
        }
        vector<vector<int>> ret(m, vector<int>(n));
        for (int i = 0;i < m;i++)
        {
            for (int j = 0;j < n;j++)
            {
                int x1 = max(0, i - k) + 1;
                int y1 = max(0, j - k) + 1;
                int x2 = min(m - 1, i + k) + 1;
                int y2 = min(n - 1, j + k) + 1;
                ret[i][j] = dp[x2][y2] - dp[x1 - 1][y2] - dp[x2][y1 - 1] + dp[x1 - 1][y1 - 1];
            }
        }
        return ret;

    }
};